This invention relates generally to a simplified apparatus and method for filling, venting and de-aerating a complex engine coolant system.
In an engine equipped with an aftercooler, it is desirable to operate the aftercooler with air at approximately 100.degree. F. In typical high flow coolant systems, one hundred percent of the stream of coolant flows through the single pass radiator when the thermostat is open. The coolant enters the radiator at approximately 195.degree. F.-200.degree. F. and exits the radiator at approximately 185.degree. F.-190.degree. F. Thus, the exiting engine coolant cannot significantly lower the temperature of the aftercooler air. To permit the aftercooler to operate closer to the desirable temperature, some manufacturers have constructed systems where a second radiator in front of the coolant radiator is provided for cooling the aftercooler air. A drawback of such systems is that in cold temperatures the aftercooler is initially fed with air at extremely low temperatures from the air radiator. Aftercooler air at such low temperatures causes inefficient operation of the aftercooler and loud knocking noises. Consequently, these manufacturers must equip their systems with a bypass for the air radiator and a pre-heater for cold weather.
Rather than equipping the engine with a preheater and a second radiator with a bypass, other manufacturers have solved the problem of lowering the aftercooler air temperature by using a low flow, multipass radiator. In a low flow radiator system, only a small percentage, such as twenty percent, of the stream of coolant enters the radiator. The remaining coolant bypasses the radiator. Because a smaller amount of coolant flows through the radiator, the coolant exits the radiator at significantly lower temperatures, such as 135.degree. F. This coolant exits the radiator and cools the aftercooler air at this lower temperature. After cooling the aftercooler air, the coolant from the radiator mixes with the coolant which has bypassed the radiator. The mixed solution then enters the engine block coolant jacket at approximately 185.degree. F. In cold weather when the thermostat is closed, the aftercooler air is warmed with coolant directly from the engine block coolant jacket.
In all radiators, it is necessary to provide a means for de-aerating the system. This need is especially true with multi-pass radiators. Without such a de-aerating means, gas may accumulate in the top header tank of the radiator. This trapped gas could cause a vapor lock in the top header tank which would consequently shut down the cooling process. Thus, to de-aerate the coolant system, a de-aerating tank is typically supplied in communication with the top headers of a multi-pass radiator. Radiator vent lines are supplied to permit the flow of trapped gas from the header tanks to the de-aerating tank.
A drawback of providing a passageway for trapped gas to exit the top header tank is that coolant may also flow from the radiator to the de-aerating tank. One must limit the amount of coolant which flows from the radiator to the de-aerating tank to prevent both inefficient cooling when the thermostat is open and excessive heat loss in cold weather when the thermostat is closed. Inefficient cooling can occur when the thermostat is open because coolant may exit from the top header tank to the de-aerating tank in the radiator vent lines and thus bypass subsequent tubes of the radiator. Therefore, the subsequent passes become less efficient in cooling the coolant. Such bypassing might cause overheating in hot temperatures. Excessive heat loss can occur in cold weather because of "backflow". When the thermostat is in the closed position, the return line to the radiator is closed and coolant from the engine block coolant jacket is initially discharged into the supply line to prevent the normal flow of coolant through the radiator. Backflow occurs when coolant flows out of the engine block coolant jacket, into the exit of the radiator through the supply line, out of radiator through the de-aerating vent lines in the top header tank to the de-aerating tank, and back to the engine block coolant jacket through the fill line interconnecting the de-aerating tank and the engine block coolant jacket. This undesired reverse coolant flow in cold weather causes excessive heat loss and may prevent the defrosting of the windows and the heating of the operator compartment of the vehicle. Preventing backflow is critical in the operation of trucks where operators may idle their vehicles for long periods of time in cold weather either in traffic or when parked on a roadside.
To limit the flow of coolant, manufacturers have used ball check valves in the radiator vent lines at the opening to the de-aerating tanks. The drawbacks of such systems are expense and unreliability. The ball check valve could easily clog from sediments which are common to a engine coolant system. Thus, the manufacturers must provide costly access holes in the de-aerating tanks to permit the cleaning of the ball check valves. Other manufacturers have avoided the expense of providing an access hole by placing manual cock valves in the middle of the radiator vent lines. A drawback of this apparatus is that the valve can be serviced only by removing the radiator vent line. Another drawback of this apparatus is that the radiator vent line must be external to the radiator and de-aerating tank which adds expense to the system. It would be desirable to have a de-aerating apparatus which is more economical, which may be internal to the system and which is easily serviceable.
Another problem with engine coolant systems, especially systems with multi-pass radiators, is the venting of the system to facilitate complete and rapid filling of the system with coolant. Because the radiator vent lines are maintained with narrow openings, the radiator vent lines do not provide sufficient venting of gas to completely and rapidly fill the coolant system.
Some manufacturers have provided a second opening to the atmosphere in the radiator to vent the system when filling it with coolant. To fill the system, a user must open a plug in the top header tank of the radiator before pouring coolant into the system through the filler neck. Because gas may vent through the unplugged vent opening, the system fills rapidly with coolant. However, drawbacks of this system are added expense in providing a second opening in the radiator system and the added procedure which an operator must follow to effectuate rapid and complete filling of the coolant system. Other manufacturers provide manual cock valves in the radiator vent lines to vent the system when filling the system. The cock valves have a fully open position which allows complete venting when filling and a partially open position which allows de-aerating during the operation of the engine coolant system. Besides having the drawback of requiring an external radiator vent line, these systems have the drawback of requiring the operator to perform additional steps to effectuate complete filling of the engine coolant system. Moreover, if the operator forgets to partially close the cock valve, excessive coolant could escape from the radiator during the operation of the engine causing inefficient cooling or excessive heat loss. If the operator inadvertently closes the valve, vapor lock could occur and shut down the cooling system.